1. Field of the Invention
The present invention relates to a transfer mechanism for a turret indexing and positioning system, in which the transfer mechanism is separated into several modules to avoid interference among the elements during assembly, thereby reducing the assembly cost and improving stability of the turret during selection of cutters.
2. Description of the Prior Art
The automatic lathe is a widely used machine. In addition to meeting the demands of high speed, high accuracy, and smooth operation, reduction of assembly cost for mass production, maintaining its reliability and precision must be taken into consideration in the design of automatic lathes so as to improve competitive capacity in the market. This is the trend of modern lathe design.
FIG. 7 of the drawings illustrates a conventional mechanism of turret index and position that already possesses the characteristics of high speed, high accuracy, smooth operation, and compactness. Yet, the production cost is still relatively high and thus adversely affects the competitive advantage in the market, as the ease of assembly is ignored.
As shown in FIG. 7, the conventional mechanism of turret indexing and positioning system includes a hydraulic motor 50 that drives a shaft 51, and a set of cam wheels 52, 56, and 57 are interconnected between the shaft 51 and an output shaft 55 to which a turret (not shown) that carries a number of cutters (not shown) is attached. A hydraulically controlled three-piece tooth-type shaft coupling 61, 62, 63 is used to instantly stop the output shaft 55 to precisely position the turret at a pre-set rotation index that corresponds to a selected cutter to be used for processing. The three-piece tooth-type shaft coupling 61, 62, and 63 initially locks the output shaft 55. When the shaft 51 is rotated, hydraulic oil enters an outer end face of a movable sleeve 61 of the three-piece tooth-type shaft coupling via an oil path 66 and makes the movable sleeve 61 to disengage from a reference sleeve 62 and a rotational sleeve 63 of the three-piece tooth-type shaft coupling. As a result, the output shaft 55 is rotatable to allow selection of the cutters on the turret. At the same time, oil enters an end face of the rotational sleeve 63 via an oil path 65 to provide a clearance between the rotational sleeve 63 and the reference sleeve 62 such that the reference sleeve 62 does not contact with the rotational sleeve 63 during rotation of the output shaft 55. When the turret reaches the desired index that corresponds to a selected cutter to be used, supply of oil is stopped to return the sleeves 61, 62, and 63 to their original positions and thus locks the output shaft 55 as well as the turret in place.
In assembly, a piston ring 59 is provided around the output shaft 55 so as to generate a clearance between the rotational sleeve 63 and the reference sleeve 62 during rotation of the turret. Hence, the piston ring 59, a bearing 58, and a follower roller disc 56 are mounted around the output shaft 55 in sequence after assembly of the sleeves 61, 62, 63, the output shaft 55, and a main body 64 that houses the elements. Then, a nut 54 is applied to secure the elements in place. In order to assure a clearance between the reference sleeve 62 and the rotational sleeve 63 during rotation of the turret, the clearance must be measured in advance, and the piston ring 59 is then moved rearwards. Assembly is proceeded after affixing an end face of the piston ring 59. This is very complicated and troublesome. In addition, the roller disc 56 must be repetitively assembled in response to the affixing procedure and the assembly procedure. As a result, the assembly is time-consuming and costly.
Furthermore, the roller disc 56 is secured to the output shaft 55 by a key 53 that might be damaged by shear forces resulting from an inertial force generated during rotation of the turret. This renders the turret to be unreliable after extended use with the automatic lathe. Moreover, the use of the nut 54 to axially secure the roller disc 56 to the output shaft 55 also requires complicated adjustment to properly position the cam 52 during assembly.
The present invention is intended to provide an improved transfer mechanism of turret index and position to solve the above mentioned problems.